格式化输出

a = "1"
b_name = "小牛牛"

# 用 %s 代替一个参数 s 是字符串str的意思.

print("my name is %s" %b_name)
print("my name is %s and my age is %s years old." % (b_name, a))    # my name is 小牛牛 and my age is 1 years old


# 用format 方法

# {}不设置指定位置, 按默认顺序
print("my name is {} and my age is {} years old".format(b_name, a))     # my name is 小牛牛 and my age is 1 years old
# 设置位置
print("my name is {1} and my age is {0} years old".format(a, b_name))   # my name is 小牛牛 and my age is 1 years old